Three drivers have been wounded by gunfire, though none of the wounds was considered life-threatening. Police have said they were looking into as many as 20 reported highway shootings, but that number has fluctuated as investigators address new reports and rule out others.

Most of the shootings were reported in an area in the southern part of Kansas City, Mo., known as the Grandview Triangle, where three interstate highways and U.S. 50 intersect. In all cases someone fired shots just before reaching a highway exit ramp or road split, then veered off in a different direction from the victim’s vehicle.

A reward for information leading to an arrest has been increased to $10,000.